Two-Dimensional Infrared Correlation Spectroscopy, Conductor-like Screening Model for Real Solvents, and Density Functional Theory Study on the Adsorption Mechanism of Polyvinylpolypyrrolidone for Effective Phenol Removal in an Aqueous Medium

Abstract

The discharge of industrial effluents, such as phenol, into aquatic and soil environments is a global problem due to its serious negative impacts on human health and aquatic ecosystems. In this study, the ability of polyvinylpolypyrrolidone (PVPP) to remove phenol from an aqueous medium was investigated. The results showed that a significant proportion of phenol (up to 74.91%) was removed using PVPP at pH 6.5. Isotherm adsorption experiments of phenol on PVPP indicated that the best-fit adsorption was obtained using Langmuir models. The response peaks of the hydroxyl groups of phenol (OH) and the carboxyl groups (i.e., CO) of PVPP were altered, indicating the formation of a hydrogen bond between the PVPP and phenol during phenol removal, as characterized using 1D and 2D IR spectroscopy. The resulting complexes were successfully characterized based on their thermodynamic properties, Mulliken charge, and electronic transition using the DFT approach. To clarify the types of interactions taking place in the complex systems, quantum theory of atoms in molecules (QTAIM) analysis, reduced density gradient noncovalent interaction (RDG-NCI) approach, and conductor-like screening model for real solvents (COSMO-RS) approach were also successfully calculated. The results showed that the interactions that occurred in the process of removing phenol by PVPP were through hydrogen bonding (based on RDG-NCI and COSMO-RS), which was identified as an intermediate type (∇2ρ(r) > 0 and H < 0, QTAIM). To gain a deeper understanding of how these interactions occurred, further characterization was performed based on adsorption mechanisms using molecular electrostatic potential, global reactivity, and local reactivity descriptors. The results showed that during hydrogen bond formation, PVPP acts as a nucleophile, whereas phenol acts as an electrophile and the O9 atom (i.e., donor electron) reacts with the H22 atom (i.e., acceptor electron).

Assessing the Performance of Al12N12 and Al12P12 Nanostructured Materials for Alkali Metal Ion (Li, Na, K) Batteries

“…For ∇ 2 (r) < 0 and H (r) < 0 it indicates a strong covalent bond, for ∇ 2 (r) > 0 and H (r) < 0 it indicates a partial covalent bond, while for ∇ 2 (r) > 0 and H (r) > 0 it indicates a noncovalent bond. As observed in Table 6 , the Laplacian of electron energy density has positive values from the studied surfaces, i.e., ∇ 2 (r) > 0; this indicates the accumulation of the electron density in the region of two bounded atoms in agreement with ref ( 39 ). It is observed from Table 6 that ∇ 2 ρ(r) > 0 and H (r) > 0 indicate a weak covalent interaction, i.e., a strong electrostatic bond, while ∇ 2 ρ(r) > 0 and H (r) < 0 indicate a medium strength or partially covalent bond since the value of H (r) is negative for the interaction between AlN–Na + .…”

Electrocatalytic activity of metal encapsulated, doped, and engineered fullerene-based nanostructured materials towards hydrogen evolution reaction

“…The Bader’s quantum theory of atoms in molecules (QTAIM) was employed to analyze the non-covalent interactions of the adsorbed hydrogen (H), and the studied systems. The quantum parameters used to expatiate the non-covalent interactions at bond critical points (BCP’s) 34 in the QTAIM analyses are the Laplacian of electron density 2 , potential energy density (V(r)), Hamiltonian kinetic energy density (K(r)), Lagragian of electron density (G(r)), density of electrons ( (r)), and total electron energy density (H(r)). Hence, the values of the extracted bond critical point parameters via QTAIM analyses are given in Table 2 , and the iso-surface of the studied systems given in Fig.…”

Insight into the photodegradation mechanism of bisphenol-A by oxygen doped mesoporous carbon nitride under visible light irradiation and DFT calculations

“…The Fukui function ( f k − and f k + ), local softness ( σf k − ), and local electrophilicity indices ( ωf k + ) are local descriptors that represent a favoured region for the mechanistic insight into the photocatalytic reaction between the photocatalysts and the BPA. 68 Chemists have used these approaches to identify which atom tends to donate or accept electrons. This study has two possible reaction mechanisms, O-MCN with BPA and MCN with BPA.…”